This invention relates to Viscosity Index Improvers (VII), and more particularly to a dispersant/antioxidant Viscosity Index Improving polymethacrylate lubricant additive.
As is well known to those skilled in the art, lubricating oils for internal combustion engines typically contain a multitude of additives which function as detergents, dispersants, viscosity index improvers, pour depressants, etc., to improve the properties of the oil. It has also been found that it is particularly necessary to improve the resistance of a lubricating oil to oxidation.
In developing suitable additives for imparting various properties to lubricating oils, polymethacrylate (PMA) polymers have been found to be useful for a variety of applications in lubricants. Some of their chief uses are as Viscosity Index (VI) improvers and pour point depressants (PPD's) for lubricants. The preparation of functionalized PMA's has increased in recent years. Many functionalized PMA's contain some amine functionality for the purpose of imparting dispersancy to the polymer. Other functionalized PMA's are also known, but a lesser extent. There are, however, only a few examples of antioxidants being incorporated into the polymers. In developing PMA's which impart multifunctional properties to VII's and lubricants an adequate process has not been developed for synthesizing a multifunctional PMA, incorporating an amine type antioxidant.
Thus, it is an object of the present invention to provide a multifunctional antioxidant/dispersant containing a polymethacrylate (PMA) VI improver for use in accessory fluids or crankcase formulation in order to increase the stability and improve the performance of such products under high temperature engine operating conditions.